In the medical practices of early days, a used syringe would be thoroughly sterilized for repeated use later. Any incomplete sterilization would dangerously cause a second time infection of a patient and/or any other people. To avoid such second time infection, disposable syringes are largely produced. However, large amount of discarded disposable syringes also bring us new problems of environmental pollution and safety of syringes in use. This is because no specific measures have been taken in disposing cannulas of the discarded syringes and exposed cannulas tend to easily stab nursing or cleaning personnel and result in even more infected people. To prevent discarded syringes and/or cannulas from unexpectedly stabbing and therefore undesirably injuring and infecting other people, including nursing and cleaning persons, many safety syringes are particularly developed, such as U.S. Pat. Nos. 5562,627; 5,405,327; 5,569,203; 5,899,887; 5,395,346, etc., all disclose syringes having specially associated hubs and barrels, so that hubs and cannulas held thereto of used syringes can be pulled back into the barrels without the risk of unexpectedly stabbing other people.
However, all these safety syringes of prior art developed to improve conventional syringes have a common issue, that is, the hubs of these safety syringes must be able to be stably connected to the barrels and be pulled back into the latter after the syringes have been used, while the hubs must be connected to the barrels in an absolutely airtight relation that is a very important factor in providing good quality safety syringes. As it is known that, when such safety syringes are assembled in the manufacturing process thereof, the hubs and the barrels must first be associated with one another before the syringes are sterilized, so that the assembled syringes would not be contaminated after the sterilization due to contact of any part of the syringes. However, the assembled hubs and barrels are subject to stress deformation and thermal deformation during the sterilization under high temperature and such deformation would have adverse influence on the stable and airtight connection of the hubs to the barrels.
It is therefore tried by the inventor to develop a further improved safety syringe to eliminate the drawbacks existing in the safety syringes of prior art.
A primary object of the present invention is to provide a safety syringe with a needle sleeve lock that is particularly made to improve a conventional safety syringe with a retractable hub. The needle sleeve lock of the safety syringe of the present invention allows the syringe to be sterilized with the hub and the barrel thereof in a contacted but non-engaged state, so that no stress deformation of the syringe would occur to adversely affect the stable and airtight connection of the hub to the barrel of the syringe after the sterilization.
Another object of the present invention is to provide a safety syringe with a needle sleeve lock, so that the needle sleeve lock firmly holds the cap, the hub and the barrel together, allowing the cannula and the hub to be isolated from external environment and protected against contamination due to any external contacting of the cannula before the syringe is used to inject. The needle sleeve lock also allows easy retaining of the hub to the barrel of the safety syringe simply by depressing the cap. And, the cap can be then pulled forward again to bring the needle sleeve lock to together separate from the syringe to expose the cannula for injection.
The needle sleeve lock of the present invention is provided at an inner wall with two diametrically opposite and radially inward projected stoppers against which two radially outward projected stoppers at rear end of the cap abut, preventing the cap from being undesirably depressed to cause undesired early engagement of the hub with the barrel before the syringe is to be used for injection.